Cultural, morphological and pathogenic variability of Phytophthora colocasiae isolate from taro in Cameroon

There exist 124 species of Phytophthora worldwide that cause serious diseases in natural ecosystems. These species have been identified using molecular methods. This study was conducted to determine the cultural, morphological and pathogenic variability of isolates of P. colocasiae processed from cultivars of Taro from Cameroon.The study was conducted in three agroecological regions, namely, Yaoundé, Bambui and Ekona where the disease was prevalent. Morphology showed that the mycelia were circular on all the isolates, in the three study zones. Mycelia colours ranged from white to cotton white. The colours of the culture media, after inoculation and mycelia growth, were the same. There was a significant difference (P<0.05) in mycelial growth among the isolate; with the longest of 5.5 cm in V6 juice agar media. Spore morphology was either spherical or ovoid in all the Taro isolates, in all culture media, except water medium. All four isolates were pathogenic to the four cultivars of Taro, causing lesions on leaves on inoculation. The most virulent fungi isolates were L1 (dark green petiole with small leaves) and L2 (red petiole with small leaves), which caused the largest lesion (>10 mm) in Taro cultivars during 14 days of inoculation. &nbsp

Impact of fungicide application on taro leaf blight disease in three regions of Cameroon

Open Access JournalThe study was conducted in the research field sites of the Institute of Agricultural Research (IRAD), Bambui, North West Region, (IRAD), Ekona South West Region and the International Institute of Tropical Agriculture (IITA) Nkolbisson, Yaoundé, Center Region of Cameroon. Four cultivars of taro (Dark green petiole with small leaves (L1), Red petiole with small leaves (L2), Light green petiole with large leaves (L3) and Light green petiole with small leaves(L4)) were planted in four seasons, for two years, in the months of March and July 2015, March and July 2016 in all the research farms. Ninety corms of the each cultivar were treated before planting with fungiforce at 0.33% concentration while others were not treated. Fungiforce is a contact and systemic fungicide containing high levels of copper oxide (600 grams) and mild levels of metalaxyl (120 grams), various concentrations of 0.4%, 0.33%, 0.27%, at the onset of the first symptom of leaf blight on the leaves using knapsack sprayer of 15 litres at two weeks interval, while the control experiment consisted of unsprayed taro leaves. Data for the disease incidence of taro leaf blight was recorded from the onset of disease in fields and continued at two weeks interval for 6 weeks. The results of planting taro in four seasons in three experimental field sites revealed that there was a decrease in disease incidence in fields sprayed with fungiforce than in the control field. Plots sprayed with fungicide at different concentrations showed no variation on the 4 cultivars in the different field sites. The disease incidence ranged from 10% to 100% in the 4 seasons, at the three experimental field sites. The variation in disease incidence in the three planting sites is an indication of possible genotypes by environment (GXE) interaction that may have significant influence on the taro leaf blight resistance potential

Effect of different doses of NPK fertilizer on the infection coefficient of rice (Orysa sativa L.) Blast in Ndop, North West of Cameroon

The developpement of fungi diseases such as Rice blast which cause important yield losses in rice cultivation in Cameroon is favorite by a variation of doses in minerale fertilisation. Since those elements facilitate the infection process and the development of pathogens. As part of the solutions to this constraint, a field trial was conducted using NPK fertilizer at three different doses, i.e., 180 kg/ ha ; 200kg/ha ; 220 kg/ha plus a control (0 kg/ha). Four rice varieties were used : NERICA 3 and NERICA 7 as upland rice varieties while NERICA 36 and NERICA 42 as lowland rice varieties. To evaluate the influence of the different doses of fertilizers (NPK),  a randomised complete block design was used. Disease parameters like incidence and severity of rice blast were evaluated at all the growth stages. Results obtained revealed that disease incidence and severity of rice blast during the vegetative growth of the different varieties of rice, was more significant on the control compared to the other treatments and lowland rice varieties were more infected than upland rice. Fertilizer N-P-K (20-10-10) at the dose 200 kg/ha makes the plant less susceptible to the blast at all its growth phases. Thus, the use of fertilizers at the proper doses is necessary for fighting against rice blast.Keywords : Rice blast, NPK Fertilizer, rice varietie

Biological versus chemical control of fall armyworm and Lepidoptera stem borers of maize (Zea mays)

Insect pests are serious constraints to production of maize. There is little information on the control measures against those insects in Cameroon. This study was carried out to identify the different species of fall armyworm and stem borers of maize and test the efficacy of different control methods. The maize variety ATP (Acid Tolerant Population) was used in a randomized complete block design. Synthetic insecticides, lambda cyalothrine and cypermethrin, were applied at one and two weeks intervals at the recommended doses of 2 L/ha and 1.5 l/ha respectively. Bio insecticides: Neem oil (Azadirachta indica), and aqueous extracts of Chenopodium ambrosioides leaves were applied weekly at the doses of 1.40 L/ha and 6.80 L/ha respectively. The different larvae recorded were the fall armyworm (Spodoptera frugiperda) and stem borers (Busseola fusca and Sesamia calamistis). All the treatments used in this study had significant effects on the number of pupae, the tunnels and the number of perforations on stems of the maize. The Neem oil at one-week interval was more effective in reducing the incidence (81, 21%) and severity (61, 54%) at 76 Days After Planting of the attack by the caterpillars as well as on the number of larvae (14, 82%) throughout the trial

Infection coefficient of Maize streak virus, leafhoppers composition and control using biopesticids and some cultural practices in agro‑ecological zones of Cameroon

Published online: 17 Jan 2022Maize streak virus (MSV) is a major threat to cereal production, hence food security in sub-Saharan Africa. The virus is spread mainly by insect vectors. The leafhoppers composition and distribution of potential MSV vectors were evaluated, and the performance of various control techniques against the vectors assessed in the major maize production areas of Cameroon. These techniques included the use of botanical extracts of Azadirachta indica A Juss. and Chenopodium ambrosoides L. Mosyakin and Clements, intercropping maize with cassava and soybean, and use of the synthetic insecticides Imidacloprid. The infection coefficient of maize streak disease and the abundance of leafhoppers were assessed in three agro-ecological zones of Cameroon (AEZs) including the Sudano-Sahelian zone (AEZ I), the Western highlands (AEZ III) and the humid forest with bimodal rainfall (AEZ V). Among 15 leafhoppers species recorded, 15 were recorded in AEZ I; 14 in AEZ III and 12 in AEZ V. The most abundant species in each AEZ was Afrosteles distans (Linnavuori) while the least abundant was Aconurella erebus (Distant). Intercropping maize with cassava and maize with soybean significantly reduced the infection coefficient of MSV in the different study zones. Also, phytochemical treatments significantly performed well with neem being the most efficient in the reduction of abundance compared to the other treatments. Thus, the use of the plant extracts and intercropping against leafhopper vectors of MSV effective